Interruptible power supply systems are apparatuses which generally provide power generated by a battery or an additional auxiliary power supply to a load in case of emergency such as a power outage. Since an uninterruptible power supply system is allowed to operate in the event of a power outage and an auxiliary power supply supplies power for several seconds to several hours, electric installations of a load are protected and electric installations normally operate.
Such uninterruptible power supply system include a central processing unit (CPU) which controls operations of converting prevailing alternating current (AC) power into direct current (DC) power to charge an auxiliary power supply such as a battery, converting DC power of the auxiliary power supply into AC power to be supplied to a load in the event of an electric discharge, and converting the DC power of the auxiliary power supply into AC power when a power outage is sensed.
However, the CPU may malfunction due to electromagnetic waves and may wrongly determine as a power outage occurs when it does not occur due to a disorder in hardware of the CPU or an error or disorder in software such as an error in a control program of the CPU. Accordingly, the CPU allows DC power of an auxiliary power supply to be converted into AC power, thereby generating a discharge of the auxiliary power supply even though a power outage does not occur.
Also, after a power outage actually occurs, since the DC power of the auxiliary power supply is not converted into AC power before the CPU determines the occurrence of the power outage and begins controlling the conversion of the power of the auxiliary power supply. Accordingly, for example, when the load is one of a network server, a hub forming a local area network (LAN), an L2 switch, and an access point, it is impossible to normally perform network communication. Also, when the load is a closed-circuit television (CCTV) camera forming a security system, since security surveillance is not normally performed, unexpected damages may occur to users.
Also, a configuration of a circuit for converting prevailing AC power into DC power to charge the auxiliary power supply and the converting DC power of the auxiliary power supply into AC power to supply power to the load becomes complicated.
As a cited reference, there is Korean Patent Registration No. 10-0778892 (registered in Nov. 16, 2007).